This invention relates generally to electronic devices and more particularly to a method and apparatus for switching high frequency signals.
Microelectromechanical microwave (MEMS) capacitive switches can be used for switching high frequency signals. Examples of microelectromechanical microwave capacitive switches are described in U.S. Pat. No. 5,619,061 entitled, Micromechanical Microwave Switching, which is incorporated herein by reference. Such switches may be used for functions such as beam steering in a phased array radar. MEMS capacitive switches generally are low loss devices because they include no active semiconductor components. The lack of active semiconductor components also makes MEMS capacitive switches relatively inexpensive.
A problem with some implementations of microelectromechanical microwave capacitive switches is that they show an inability to remain in a switched on position for more than a few seconds at low frequency bias voltages and show a bipolar response when exposed to high-frequency bias voltages. Bipolar response refers to switching on at both zero and positive bias.
Accordingly, a need has arisen for an improved method and apparatus for method and apparatus for dielectric charges reduction in micromechanical microwave capacitive switches that address shortcomings of prior methods and apparatuses.
According to one embodiment of the invention, a method of forming a switch includes providing a conductive region, a membrane, and a dielectric material. The method includes disposing a region of the dielectric material between the conductive region and the membrane such that a sufficient voltage applied between the conductive region and the membrane effects a capacitive coupling between the membrane and the conductive region. The dielectric material has a resistivity sufficiently low to inhibit charge accumulation in the dielectric region during application of the voltage.
According to another embodiment of the invention, a switch includes a conductive region, a membrane, and a dielectric region. The dielectric region is formed from a dielectric material and is disposed between the membrane and the conductive region. When a sufficient voltage is applied between the conductive region and the membrane, a capacitive coupling between the membrane and the conductive region is effected. The dielectric material has a resistivity sufficiently low to inhibit charging in the dielectric region during operation of the switch.
Embodiments of the invention provide numerous technical advantages. For example, in one embodiment of the invention, a switch is provided that does not suffer from bipolar operation in response to high frequency stimulus and does not turn off inadvertently when it should be turned on in response to low frequency stimulus, which are disadvantages associated with some prior devices. Further, according to the invention, a switch is provided that can be repeatedly activated in response to a bias voltage having a fairly constant magnitude. Such switches provide more reliable operation and are desirable. Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.